Chemical reactions, such as for example highly exothermic reactions, have the characteristic that they release a large amount of heat. Such a highly exothermic chemical reaction is for example, in simple terms, a liquid-liquid reaction of at least one first component, which is denoted for example by A and in particular in liquid form, with at least one second component, which is denoted for example by B and in particular in liquid form, to form at least one reaction product, which is for example in liquid form and denoted by C. The reaction heat released per unit of time in the process is proportional to the rate of the reaction, which is dependent inter alia on the concentration and thus the degree of mixing of the components, also referred to as reagents or reactants. In other words, the components A and B are commonly also referred to as reactants, wherein the reaction product is commonly also simply referred to as product.
In order to allow the reactants to chemically react with one another, the reactants are mixed with one another. Here, if mixing of the reactants occurs too quickly, then the resulting release of heat owing to the chemical reaction may be more rapid than the dissipation of heat by heat conduction and/or convection within the reaction mixture and heat conduction through a reactor wall to a coolant, which leads to a temperature increase. In the opposite situation, in which the mixing occurs too slowly, temperature peaks owing to the local reaction cannot be dissipated by convection, which leads to local overheating of an interface between the reactants. Both phenomena lead to overheating of the reaction mixture and, in association with this, to undesired chemical byproducts and/or to thermal decomposition of the reagent and product molecules. This is also referred to as “reaction runaway”. This conflict can be resolved by means of an advantageous degree of mixing with targeted dosing for example of the second component to or into the first component, wherein, with this degree of mixing, the specific heat power released is still uncritical owing to limitation of an inflow rate of a reactant but, at the same time, local overheating owing to inadequate mixing can be avoided.
In order to allow the reactants to mix and thus chemically react with one another, use is commonly made of a reactor, also referred to as reaction apparatus. If the reaction takes place under high pressure, vessel walls of a reaction apparatus should have a particular wall thickness in order to prevent rupturing of the reaction apparatus, also referred to as vessel. Thick or large wall thicknesses however lead to a high thermal resistance with regard to an exchange of heat between a coolant and the reactants and/or the product, whereby, for example in the case of a highly exothermic reaction, a desired dissipation of heat from the reactants and/or from the product to the coolant is impeded. If it is sought for the reactants and/or the product to be warmed by a medium in the form of a fluid, for example, a heat transfer from the medium via the vessel or the vessel walls to the reactants and/or the product is likewise possible only with very low effectiveness. In more general terms, use is for example made of at least one medium, in particular in the form of a fluid, by means of which it is sought to influence a temperature of the reactants and/or of the products such that an exchange of heat between the medium and the reactants and/or between the medium and the product occurs. Such an exchange of heat can be adversely affected by excessively large or thick wall thicknesses.
Furthermore, materials from which the vessel is formed should be corrosion-resistant with respect to the reagents, the product and any byproducts that form, and the medium and any other agents that come into contact with the vessel, such as cleaning and/or rinsing liquids. Depending on chemical reactivity, use is normally made of only special alloys such as high-grade steels, nickel-based, hafnium, niobium, zirconium or tantalum alloys for the materials, wherein these are often difficult to manufacture and/or to weld and thus limit the degrees of freedom with regard to the design of the vessel, in particular the geometry thereof.
The form or geometry of the reaction apparatus is normally dependent on physical-chemical parameters of the components involved. The physical-chemical parameters are for example thermal conductivity and heat capacity of the reagents and/or of the product, of the medium and of the material from which the reaction apparatus is formed. Furthermore, the physical-chemical parameters and fluid dynamics characteristics of the reagents and of the product may be decomposition temperatures of the reagents, of the product and possibly of the material from which the reaction apparatus is formed.
Furthermore, the form of the geometry of the reaction apparatus may be dependent on the reaction characteristics such as reaction enthalpies, optimum reaction pressure and temperature, temperature-dependent and concentration-dependent reaction kinetics, and existence and relevance of secondary reactions and of process parameters such as for example mass flows of reagents and medium and additional pressure loss.
Although the challenges for reactor design are extremely complex, the development of present reactor concepts is limited primarily to simple geometries and is driven predominantly by experimentation. Non-optimal reactor geometries may lead to reduced reaction throughputs, impure products, increased coolant usage and larger reactor dimensions than would be necessary in the case of a particularly advantageous or optimal design. A design targetedly directed to the above-stated parameters and the combinations thereof followed by a targeted construction is realized only in very rare cases, and then also normally using standard components.